Background. Respiratory syncytial virus (RSV) is the most frequent etiologic agent causing lower respiratory tract infection in children <2 years of age. Between 0.5 and 3% of patients will require hospitalization. The aim of this study was to estimate the direct medical cost of treating children <2 years old with suspicion of RSV at the Instituto Mexicano del Seguro Social (IMSS). Methods. Direct medical costs were estimated from an institutional perspective. Medical records were reviewed from patients <2 years of age who attended emergency services in second-level hospitals including subjects who required hospitalization. Estimated costs were obtained with the microcosting technique using the institutional costs from IMSS (year 2010). Costs were reported in USD (year 2011). Results. When analyzing total medical costs, outpatient management yielded a cost of $230.0 ± $10.30 U.S. dollars (USD), whereas hospitalized patients exhibited an average cost of $8,313.20 ± $595.30 USD. The main components of outpatient management costs were emergency visits, specialist consultations and diagnostic testing (41.6%, 32.7% and 10.7% of the total cost, respectively). In the case of hospitalized patients, intensive care unit cost (89.3%) and overall hospitalization cost (6.5%) represented 95.7% of the total cost. Conclusions. RSV is a disease that represents a significant economic burden for health care institutions, although most patients are treated on an outpatient basis.